1. Field of the Invention
The present invention relates to a membrane nitrogen gas generator with improved flexibility, which is capable of providing an increased flow rate during periods of high demand.
2. Description of the Background
Membrane processes are used with increasing frequency in the production of inert gases from atmospheric air, wherein the oxygen content in the feed air stream through the membrane is decreased by permeation to a low pressure side. Membrane nitrogen generators are most frequently used in cases where customer applications can withstand a small amount of oxygen in the atmosphere, such as, for example, from 0.5 to 5% by volume oxygen.
However, it is difficult to select an appropriate sized membrane generator for customer demand as it is not easily predicted. For example, customer demand patterns are generally not well known, and even if they are they may often change considerably both in the short term, such as, for example, at ten minute intervals, as well as in the long term, such as with the change of seasons and from one year to the next. Of course, this difficulty is not specific to membrane processes, but to any small on-site plant serving the needs of a single customer.
At present, one method of overcoming this difficulty is to produce inert atmospheres at a pressure higher than is required by customer demand and storing excess production in a buffer tank during load demand periods for release in peak demand periods. Another method entails the use of bulk storage tanks to supplement generator production during peak demands.
While these solutions address the problem of variable customer demand to some extent, however, it remains necessary to use an oversized generator when using these processes. Unfortunately, the overall process economy is thereby impaired, particularly when annual use of the facility is low.
Hence, a need exists for a membrane generator, particularly a membrane nitrogen generator, having an improved design which specifically addresses the needs of customers having high variable flow demand patterns in an economical manner, and, in particular, which is capable of providing an increased flow rate during periods of high demand.